Chem Path: AKI and CKD Flashcards
How is creatinine used to stage AKI
Constant measurement of sCr to see how it changes. One off measurement is not useful, Stages 1 2 and 3
What is the hallmark of pre renal AKI
Reduced renal perfusion
Why can there be reduced renal perfusion
True volume depletion - dehydration, D&V, bleed
Hypotension
Oedematous stress such as HF
Renal ischaemia such as renal artery stenosis
Drugs
What drugs affect renal perfusion and how so
NSAIDs and calcineurin inhibitors - Decrease afferent arteriole dilatation
ACEi and ARBs - Decrease efferent arteriole constriction
Diuretics - Decrease preload and affect tubular fx
What is normal serum creatinine levels?
59 - 104 males
49 - 84 females
How does pre renal AKI differ from Acute Tubular Necrosis (ATN)
Pre renal AKI will resolve once the cause is addressed and the circulation volume is restored. Prolonged injury causes hypoxic necrosis and can lead to ATN. ATN does not respond to recirculating volume.
What can you see on ATN urine microscopy
Epithelial cell casts
Why would you see hydronephrosis on kidney USS
Benign prostatic hypertrophy can cause lower obstruction and there this can lead to hydronephrosis of the kidney.
What can cause post renal AKI
Physical obstructions at any levels:
Extra luminal - Mass, ovarian carcinoma pressing on ureters
Intra luminal - Stones
Prostate or urethra obstruction
What is the pathophysiology of obstructive uropathy
Massive decrease in GFR due to loss of gradient, hydronephrosis. Usually is relieved with obstruction relief
What can prolonged obstruction cause
Glomerular ischaemia
Tubular damage
Long term interstitial scarring
What can cause direct tubular injury
Ischaemia - ATN
Endogenous toxins - Myoglobin and immunoglobulins in myeloma
Exogenous toxins - Aminoglycosides (Gentamicin), aciclovir, amphotericin
What happens in rhabdomylosis
Myoglobin damage. A lot of bruising and dark (almost black) urine. Give patient a lot of fluids to wash out the myoglobin.
How does systemic vasculitis present?
Widespread purpuric non blanching rash. AKI with glomerulunephritis and vasculitis
What can cause abnormal protein deposition in renal tubules?
Amyloidosis, Lymphoma and myeloma related renal disease
What 2 parameters are used to quantify severity of AKI
Serum creatinine and urine output
Why does AKI progress to CKD?
First you stop the damage and/or bleeding. Next there is the inflammation cascade and scar tissue formation. Then the scar tissue needs to be remodelled to functional viable tissue. There is progress to CKD when there is an imbalance between scarring and remodelling.
How is CKD staged?
Stages 1 to 5 based on GFR and albumin:creatinine ratio
What causes CKD
Diabetes, hypertension, obstructive uropathy, atherosclerotic renal disease, chronic glomerulonephritis, polycystic kidney disease
What hormones does the kidney produce?
EOP for RBCs, RAS, 1 alpha hydroxylase for vit d synthesis
How does CKD cause a dysfunction. of the kidneys metabolic function?
It can cause metabolic acidosis and hyperkalaemia. Acidosis can cause muscle and protein degeneration and needs to be treated with oral sodium bicarbonate. Monitor patient levels to maintain above 20mmol/L
Hyperkalaemia can cause muscle depolarisation in cardiac and muscle function.
What ecg changes can be seen in hyperkalaemia
Flattened p waves and tall peaked t waves. Prolonged qrs complex. Can lead to VT
What medications can cause hyperkalaemia
ACEi, potassium sparing diuretics, spironolactone
How is there anaemia in CKD
Kidneys stops producing EPO when GFR < 30ml/min. This results in normocytic normochromic anaemia. You can treat with EOP alpha or beta or darboprotein
What anaemia do you see in iron deficiency
Microcytic, hypochromic
What anaemia do you see in b12 folate deficiency
Macrocytic, reticulocytes
How does CKD lead to hyperparathyroidism
Kidneys cannot excrete PO4, this will cause activation of FGF23 and Klotho which lowers vitamin D. Since there is no alpha hydroxylation of Vit D, PTH production will increase to get rid of PO4 and increase vit D production.
How does CKD lead to hypocalcaemia
Increased phosphate will form complexes with free calcium, therefore reducing serum calcium levels. Lack of Vit D leads to less calcium too.
What does CKD lead to eventually in terms of PTH
Tertiery hyperparathyroidism as the bones become resistant to the high levels of PTH.
What are 3 types of bone diseases caused by CKD
Osteoitis fibrosa cystica, osteomalacia and adynamic bone disease
What happens in osteoitis fibrosa cystica and what can you see
Increase osteoclastic reabsoprtion of calcified bone and formation of fibrous tissue.
Cystic lesions
What is adynamic bone disease
Due to overtreatment and oversupression of PTH. Leads to reduced turnover and reduced osteoid.
What happens in CKD and cardiovascular disease
Heavy calcification of arteries instead of cholestrol rich atheromas
What are the 3 stages of uraemic cardiomyopathy
LV hypertrophy
LV dilation
LV dysfunction
How do you treat excess phosphate?
Diet control and phosphate binders
What are some vit D activators
1 alpha calcidol
Paricalcitol
What are some direct PTH suppressors
Cinacalcet which works by increasing calcium sensing receptors
